Is a universal oxygen sensor really universal?
July 31, 2006 4:55 PM   Subscribe

ScoobyFilter: It's time to replace the oxygen sensors in my 2001 Subaru Outback. "Universal" replacements run about half the cost of the OEM version. Am I asking for trouble by taking the cheap way out?

I drive a 2001 Outback VDC with the H6 engine. It takes three O2 sensors -- two before and one after the catalytic converter. They're all the four-wire type. The car has 165,000 miles already so the less money spent the better.

Surfing the 'net suggests I have two options -- go with OEM-style sensors for about $100 each, or "universal" 4-wire sensors for under $50. The OEM-style sensors come with a Subaru-style plug attached, while the universal ones require I reuse the existing connector and do some splicing. I have the car's electrical diagrams and pinouts so that shouldn't be a problem.

Financially, universal sounds like the way to go but I'm hesitant. First, I read an article suggesting some cars require slightly different sensor heater currents and therefore shouldn't use universal sensors -- this was in an article about BMWs, though and I don't know if this applies to Subarus. Also, universal sensors seem to be rarer than the OEM style (e.g., my local parts stores don't carry them.) If AutoZone has no problem selling discount replacement brake pads, why don't they carry discount replacement O2 sensors? I'm worried that it might be because they're no good.

So does anybody know if universal is good enough for my make/model, or do I have to spring for the OEM type?
posted by Opposite George to Travel & Transportation (8 answers total)
I think the heater current explanation is bullshit, but if you want to be (pretty) sure, buy a Subaru sensor and a universal sensor, and measure the resistance of the heater. If its within 5% or so, return the sensor to your Subaru dealer (that's the value-add of a dealer parts department!), and buy two more universals.

Back when I had a car, I would do the same thing, but I found that the Bosch sensor made for a Ford somethingorother was even cheaper than the universal sensor. It had four wires, even. Worked fine.

As an aside, if someone who knows wat he's talking about comes along, I'd like to know how the 4-wire O2 sensor came about, and why grounding the heater to the exhaust is insufficient.
posted by Kwantsar at 5:03 PM on July 31, 2006

Also, they are a bitch to solder. I recommend stripping about 1.5" from both, scuffing the wire with fine sandpaper, twisting all the length together, soldering, and using good heatshrink.
posted by Kwantsar at 5:09 PM on July 31, 2006

why grounding the heater to the exhaust is insufficient.

Corrosion prone area, ruins ground connection quickly.
posted by IronLizard at 5:33 PM on July 31, 2006

you don't need to solder. when i got the universal ones (bosch) they came with little crimp sleeves. i'd like to tell you they worked fine on my neon, but they didn't. but i don't think they were the problem, though i never did figure out what the problem was, so i can't be sure that they actually did work. ymm (literally) v.
posted by sergeant sandwich at 5:33 PM on July 31, 2006

Go for the universal - I replaced my (old Volvo) sensor with a Bosch that was meant for a mustang (and less than 1/3 of the price), and have had absolutely no issues. I soldered mine, but it would probably be better to do a crimp/twist-on clamp connection for durability.
posted by sluggo at 6:47 PM on July 31, 2006

When working with bare wires, crimp *and* solder if they're not twist/clamp crimps. If you just crimp it, chances are it'll come loose shortly from vibrations.
posted by SpecialK at 7:28 AM on August 1, 2006

Subaru has issued recalls (.pdf) on O2 sensors for some 2001 models. I'd investigate whether yours are the subject of a service bulletin. If they are, you might get one or more factory sensors for free.
posted by Kirth Gerson at 7:30 AM on August 1, 2006

I'll second the good sergeant: the Bosch universals come with a nifty little set of connectors that fit in a larger, locking connector. No soldering necessary, and it will make a really strong connection.

The heater is only used to get the sensor up to temp quickly. Exhaust heat will take over shortly after. I wouldn't sweat it.
posted by kableh at 7:43 AM on August 1, 2006

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